Purification of metallic compounds.



acid forming metals, such as tungsten, molybcommercial yalue in the elimination, from CHARLES VAN BRUNT, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

PURIFICATION OF METALLIC COMPOUNDS.

Specification of Letters Patent.

Patented. Dec. 17, 19.07.

Application filed July 12,1906. Serial No. 325,938.

To all whom it may concern:

Be it known that I, OHARLEs VAN BRUNT, a citizen of the United States, residing at Schenectady, county of Schenectady, State of N ew York, have invented certain new and useful Improvements in the Purification of Metallic Compounds, of which the following is aspecification.

This invention relates to the purification and treatment of metals and metallic compounds, and particularly to compounds of the denum, tantalum, vanadium, chromium, etc.

According to my process, a solution of one of these metals is precipitated by an organic base to yield a precipitate of such physical characteristics that it may subsequently be treated to yield pure metal of superior quality. Furthermore, the precipitating operation is carried on fractionally to secure a high degree of purity in the final product.

The original research now being carriedon with the view to using tungsten, molybdenum, tantalum, and other high melting metals for incandescing lamp filaments has practically revolutionized the chemical knowledge as to these elements, and has conclus ively proved that, like other better known metals, the physical and metallurgical characteristics of these metals are greatly influenced by even small quantities of impurity, though the effect ismore marked in the case of the high melting metals because of their high atomic weight.

Tungsten has been used for metallurgical purposes for a long time and tungsten of commercial purity, as well as tungsten compounds such as the trioxid, can be produced without great difiiculty. The lamp filament art, however, demands something better than commercial purity, for even the most minute traces of such elements as arsenic or iron are likely to ruin the material for use in lamp filaments. My present invention is of great use and compounds "ofiacid forming metals, of the very minute, traces of impurities which are likely to be present; but in addition'to this it yields a'fpr'oduct of shiooth, even texture especially adapted for lamp filament manu facture.

In a plying my invention to the purification 0 tungsten trioxid, W0 I first prepare a solution inwhich this oxid becomes an 1 alkaline tungstate. This may be done by fusing the oxid in alkali, such as Na CO or by boiling it with an alkaline solution, as the original material may require. I next filter the solution and acidify'with HOl to neutralize the alkaligand put the solution in such condition that a preci itate of the desired character will ultimate y be produced The gplantity ofacid to be used is difficult to dee, but in general I aim to add it in such quantity as to give approximately a molecular ratio I consider .that considerable care must be :used at this step inthe process, as small variations, say .2 or :3 from this ratio appear to influence the character of the first fraction of the precipitate quite strongly. If care is used the product is entirely reliable and is characterized by the ease with which it may be washed and filtered. a

The acidified solution above described is fractionally precipitated by a solution of benzidin-hydrochlorid,

The impurities present a pear to be largely concentrated in the first action, the size of which is made dependent upon the amount of such impurities in each case. In eneral it will not exceed the tenth part of a l 'WO present and may be much less. fraction is figured to contain the bulk of the WO and is to be regarded as pure. necessary, however, that all of the VVO should not be precipitated, sincean excess of the precipitant tends to carry down impuri- The second I It is a ties which otherwise remain solution."

The tungsten precipitate is 'benzidin metatungstate O l-I (NH .4WO .X-H O. Thehydration is small, and probably varies some-- what with the conditions of precipitation etc. I next proceed by thoroughly'washin the benzidin-ztungstate with water and ca cining at a low temperature in an unglazed porcelain crucible. The low-temperature of calcination is of great practical advantages as it prevents any troublesome action of the compound on the walls of the crucible or container.' As the result of this calcination the ,water and organic material of the comound pass away,'leaving only pure W0 or reasons which I will not attem t to set forth, this WO differs physically cm the crude WO with which the process wasbegun.

It is very much finer, and in fact is an impalpable powder almost fluffy in lightness.

find that owing to this it is a most excellent product for use in the production of pure tungsten lamp filaments, or of tungsten powder to be used therein and that filaments prroduced from these materials are strong,

ee from cracks and im erfections, and for a short time, at least, operate at a temperature corresponding to an electrical in ut of only a few tenths of 0. watt per candle.

' The pure tungsten powder above mentioned may be obtained from the WO by reduction with H or by other methods of reduction and is exceedingly fine grained and uniform.

In purifying I am dealing with impurities amounting to less than one-half of 1% or even less than .1 of 1% and aside fromthe fact that my process yields an absolutely pure product, it

1s for other reasons a su erior process.

' According to well known met ods, the elimination of .1 of 1% can be effected only by repeated evaporations and crystallization, processes which in themselves require time and care, and which must be repeated again and again to secure the desired results. One

to two weeks is ordinarily required for such a treatment,- while with my process a com plete batch of onid can be purified in a single I have described my process as applied to tungsten and its OXld, but I consider my,

process as broadly applicable to acid forming metals.

Although organic bases have not been generally used in connection with the preclpitation of inorganic materials, I do not consider that this would prevent a person skilled in the art from successfully applying this invention. The benzidin referred to, although not commonly regarded as a precipitating agent, is nevertheless a common material, being used as a base for the substantive dyes. The production and some of the characteristics of benzidin are mentioned in Watts Chemist that its preparation and t e preparation of 'benzidin hydrochlorid offer no particular difliculty.

What I claim as new and desire to secure by Letters Patent of the United States, is,-.- a 1. The process which consists in forming the WO as above described,

and I consider a solution containing a com ound of an acid forming metal, fractional y precipitating this solution with an organic base, and calcining one of said precipitates to produce a pure oxid of themetal. I

2. The process which consists in forming a solution 'containin an acid forming metal, fractionally precipitating the solution with a benzidin compound, and calcining one of said precipitates to produce a pure oxid.

3. The'process which consists in producing a solution of a tungsten compound,-elimi-- nating im urities therefrom by precipitating with enzidin hydrochlorid, and then producing pure tungsten trioxid from the treated solution.

4. The process which consists in forming an alkaline solution of a compound of an acid forming metal, neutralizing said solution, precipitating with anorganic base, calcining the precipitate and reducing the calcinatlon product to produce a finely divided pure refractory metal.

5. The process which consists in preparing a solution-containing an acid forming metal, precipitatingthe solution with a benzidin compound, calcining the precipitate and reducing the calcination product to produce a finely divided refractory metal.

6. The process which consists in preparing a solution containing tungsten, purifying the solution by precipitating with .benzidin hydrochlorid, then separating a pure tungsten compound from said solution, calcining said com ound and reducing the same to obtain a 'gh melting metal powder.

7. The process which consists in the preparation of a solution containing tungsten, fractionally precipitating the solution with benzidin hydrochlorid, and calcining one of said precipitates to obtain a pure oxid.

8. The process which consists in pre aring a solution of an alkaline tungstate, aci ifying the solution, fractionally precipitating the solution with benzidin hydrochlorid, and calcining one of said precipitates to produce tungsten trioxid.

In witness whereof, I have hereunto set my hand this 11 day of July, 1906.

' CHARLES VAN 'BRUNT. Witnesses:

BENJAMIN B. HULL, HELEN ORFORD. 

